The present invention relates to a heat treatment method and apparatus for heat-treating an object of treatment in a vertical processing tube.
Conventionally, in manufacturing processes for semiconductor devices, for example, various heat treatment apparatuses are used to form oxide films, thermal CVD films, high-purity, high-density regions by thermal diffusion, etc. on objects of treatment, such as semiconductor wafers, LCD substrates, and the like.
According to modern semiconductor processes, circuits are becoming finer and finer, and the wafer diameter tends to increase, i.e., from 8 inches to 12 inches. Besides wafers, large-sized substrates, such as LCD substrates, require the aforesaid heat treatments. In order to treat these objects having relatively large areas with high accuracy, the in-plane treatment characteristics of the objects must be equalized. To this end, in the various heat treatment apparatuses, the in-plane temperature distribution of the objects should be made uniform.
As the area of each object increases, however, more heat is released from the peripheral portion of the object than from the central portion. The larger the object area, therefore, the greater the difference in temperature between the central and peripheral portions of the object is. Thus, the uniformity of the in-plane temperature distribution of the object is lowered.
The various heat treatment apparatuses are expected to be improved in throughput. Since the object of treatment has a large area, however, it sometimes slips and warps as its temperature is quickly increased to a predetermined processing temperature. If the object temperature increases at high speed, the difference between temperatures at the central and peripheral portions of the object becomes very large in some cases.
In order to ensure the uniformity of the in-plane temperature distribution of the object, moreover, the object temperature must be measured accurately.